Stir together whiskey, simple syrup, bitters, and ice in a cocktail shaker until chilled. Coat inside of a chilled 3 1/2-ounce glass with liqueur; pour out excess. Rub lemon rind strip over rim, and place in glass. Strain whiskey mixture into prepared glass.
Drop In: Tarragon. The dainty, aromatic plant and Herbsaint—a key ingredient in this Southern concoction—share sweet licorice undertones.